A dimming controller is only really necessary when you want proportional control with a light bulb. This way, the light bulb dims as the power to it changes. Otherwise the light would "pulse" - blink on and off - which is annoying. As stated, you can use dimming on any heater. So get a dimming controller if you think you might use it for a light bulb someday.

(Dimming does blink on and off, but faster than your eye can discern. Pulse blinks on and off but more slowly.)